Purchase offer is in effect

Billionaire investor Kirk Kerkorian’s offer to up his stake in Tesoro is on.

Kerkorian’s Tracinda Corp. is offering $64 a share with the hope of acquiring more than 21.8 million shares. D.F. King & Co. Inc. is handling the offer for shares if anyone wants to make a sale. The offer for purchase expires at 10:59 p.m. local time Dec. 6.